Cancer is one of the most widespread diseases and a leading cause of death worldwide. In the United States alone, cancer is the second leading cause of death, surpassed only by heart disease. Cancer is often characterized by deregulation of normal cellular processes or unregulated cell proliferation.
Multiple myeloma (MM) is a progressive and malignant neoplastic type of cancer originating from plasma cells. It is characterized by abnormal accumulation of malignant plasma cells within bone marrow, and it accounts for approximately 13% of all hematologic cancers (Palumbo and Anderson, 2011). In 2015, about 26,850 new cases were expected to be diagnosed with MM, and about 11,240 people were expected to die from the disease in the United States (ACS, 2015). The incidence of MM has increased steadily due to increased life expectancy of the general population in the United States (Warren et al., 2013). The disease most commonly affects the elderly population, with the median age of incidence around 69 years old (Howlander et al., 2013; ACS, 2015).
The therapeutic goals of management of MM are to provide symptomatic relief, achieve disease control and provide prolonged remissions (Kurtin, 2013). Conventionally, a combination of high dose chemotherapeutic agents (melphalan, vincristine, cyclophosphamide, doxorubicin, liposomal doxorubicin, bendamamustine) followed by autologous stem-cell transplantation (ASCT) has been utilized to treat young, treatment-naïve and medically fit patients (less than 65 years of age) (Palumbo et al., 2011). Age, comorbid conditions and geriatric assessment are the major criteria for deciding patients' eligibility to tolerate high-dose therapy (HDT) followed by ASCT (Palumbo et al., 2014). For elderly patients ineligible for HDT and ASCT, melphalan plus prednisone had been the standard therapy for several decades (Palumbo et al., 2011; Rodriguez et al., 2012). During the last decade, treatment algorithm of MM underwent a paradigm change with the introduction of novel immunomodulatory agents (such as thalidomide, lenalidomide, and pomalidomide) and targeted proteasome inhibitors (bortezomib and carfilzomib) (Richardson et al., 2007; Dmoszyńska, 2008; Gupta et al., 2013).
Carfilzomib is a tetrapeptide epoxy ketone proteosome inhibitor that binds selectively and irreversibly to the constitutive proteosome and immunoproteosome. More specifically, the epoxyketone electrophilic warhead binds to the catalytic threonine residue of the β5 subunit of the proteasome protein. CFZ is well tolerated with acceptable toxicity profile. Carfilzomib, polymorphic forms, methods of making, formulations, its use and other carfilzomib attributes are described in US20050245435, US20140105921 and PCT publications WO2006017842, WO2009045497, WO2014169897, WO2013169282, WO2014011695, WO2006063154, WO2014015016, and WO2010048298, each specification of which is hereby incorporated herein by reference in its entirety.
Carfilzomib has shown an encouraging response rate in patients with relapsed and refractory MM and with newly diagnosed patients with MM. To this end, carfilzomib was first approved (as Kyprolis®) for treatment in patients with relapsed and refractory MM in July 2012 as a single agent therapy. More recently Kyprolis was approved in combination with lenalidomide and dexamethasone (July 2015) and in combination with dexamethasone (January 2016) for the treatment of patients with relapsed and refractory MM who have received one to three lines of therapy. The approved treatment regimen for carfilzomib is to administer it to the patient by infusion, either over a short 10 minute period or over a slower, longer 30 minute duration of time. This infusion is to occur for 2 consecutive days per week for three consecutive weeks in a 28 day cycle. Thus, to comply with this treatment schedule, patients need to drive or be driven two times per week on consecutive days to an authorized drug administration center, such as a doctor's office, a clinic or a hospital, where carfilzomib can be properly and safely administered. This may be inconvenient or impractical, or may simply be a burden, to some patients, increasing the likelihood of reduced or decreased compliance with, or even complete non-compliance of, the full and complete course of the prescribed carfilzomib therapeutic regimen.
Carfilzomib is rapidly metabolized and cleared in humans. Carfilzomib, a small tetrapeptide compound, exhibits a short half-life in-vivo of about 60 minutes or less in humans. One mechanism of carfilzomib clearance is via hepatic blood flow, resulting in the relatively brief half-life for carfilzomib. Drug products possessing short half lives or rapid clearance in general tend to exhibit reduced target coverage leading to decreased and/or shortened biological inhibitory activity. To overcome such shortfalls, additional drug is typically administered to provide more drug and prolonged efficacy at the biological site of action. Hence, both the rapid clearance and the twice weekly frequency of dosing of carfilzomib leave room for possible improvements in efficacy, delivery and/or patient compliance.
Carfilzomib, as currently approved (Kyprolis®), is a sterile lyophilized formulation comprising sulfabutylether beta cyclodextrin (SBECD) and a sodium citrate buffer. The lyophilate is reconstituted with sterile water, and infused or injected into the patient. The SBECD excipient acts primarily as a solubilizing additive for carfilzomib, and forms a complex with carfilzomib thereby improving carfilzomib water solubility.
History has revealed that attempts to solve weaknesses of drug products have led to the preparation of alternative forms of these medicinal compounds, including production of pro-drug versions, in attempts to enhance their drug pK and/or PD properties. For instance, Greenwald et al disclose Prodrugs of Amine Containing Compounds (J. Med. Chem., 1999, 42, 3657-3667). WO2005063777 discloses benzylphosphate and substituted benzylphosphate prodrugs for the treatment of pulmonary inflammation. WO20090152160 discloses inhaled carbaprotacyclin and prostacyclin prodrugs for the treatment of arterial hypertension. US patent publication no. 20040100225 discloses acyloxymethyl pro-drugs of imatinib (Gleevec®). Also, PCT publication WO2011084846 discloses acyloxymethyl pro-drugs of risperidone. These pro-drug disclosures teach alkyl-acyloxymethyl linked pro-drugs. Another example, US patent application publication no. US20140105921 describes carfilzomib and other epoxyketone proteasome inhibitor pro-drugs having an acyloxymethyl linker connecting the inhibitor to polyethylene glycol units (PEG). However, these carfilzomib pro-drug compounds have been found to release quinone methide byproducts during metabolism in vivo, which may be potentially toxic and may present a safety risk. To this end, it would be desirable to identify alternative forms of carfilzomib and/or alternative ways to deliver the active pharmaceutical ingredient carfilzomb to patients while maintaining or possibly improving the efficacy and/or safety of the currently approved carfilzomib treatments.